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Subject: Transparent World colour in mirror reflection

keppel opened this issue on Feb 13, 2014 · 8 posts

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keppel ( ) posted Thu, 13 February 2014 at 6:01 AM · edited Tue, 01 October 2024 at 3:36 AM

Does anyone know of a method that can render only the objects in a reflection without the World colour being included?

I have the render layer set up to render only the mirror and the objects. I have the Output set to RGBA and the "transparent" checkbox ticked in the Film panel.

In the picture attached the top image is the render from Blender, and the bottom picture is what I want to get.

Rendering in Blender 2.69 using Cycles with a glossy shader on the mirror.

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Cybermonk ( ) posted Thu, 13 February 2014 at 1:36 PM

Dude I wish i could help ya. I'm trying to come to grips with cycles myself. If I come across something I'll let ya know.

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heddheld ( ) posted Thu, 13 February 2014 at 2:04 PM

thought it would work with light paths

but not made what you want work !!

can do the cant see the "vampire"

but not the vampire and nothing else lol

maybe the compositing nodes will help with different render layers

keppel ( ) posted Thu, 13 February 2014 at 8:45 PM

I'm doing some freelance work with a real estate agent who sends me pictures of vacant properties and I add virtual furniture to the various rooms. The attached image is an example of what I am doing and also illustrates the reason for my question in this thread.

The original photograph shows a mirror on the wardrobe door. When the virtual furniture is added with the Blender world colour set to the rooms paint colour the reflection that I get in the mirror matches the colour tone of the room but the reflected details of the actual room in the original photo are gone in the overlay. Having a transparent world colour in Blenders reflection renderlayer would save alot of editing and manipulation of the Blender render in Photoshop.

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Touchwood ( ) posted Fri, 14 February 2014 at 7:49 AM · edited Fri, 14 February 2014 at 7:51 AM

Not proficient by any means with Cycles but have you tried using a colour mask in the node setup to block out the world colour? I think I remember a tutorial by either Andrew Price at Blenderguru or Sebastian Konig at Blendercookie demonstrating the method.

keppel ( ) posted Fri, 14 February 2014 at 9:16 AM

Attached Link: Best Practices for Masking

Thanks for the tip Touchwood, it put me on the right path. I did a search for masking in the compositor and found the attached link which will prove helpful. It uses the difference, colour and distance nodes in the compositor to mask the selected colour.

In my situation this method has its limitations as it is removing the colour post render. This means that if any of the objects being rendered in the mirror have the same colour as the world colour then those colours get removed as well. If I change the world colour to something that is different to the rendered objects in order to create a clean mask it leaves an incorrect colour tint on the rendered reflected objects.

Again thanks for the help.

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